linux-user: Simplify host <-> target errno conversion using macros

linux-user: Simplify host <-> target errno conversion using macros

Convert the host_to_target_errno_table[] array to a switch
case to allow compiler optimizations (such noticing the identity
function when host and guest errnos match). Extract the errnos
list as to a new includible unit, using a generic macro. Remove
the code related to target_to_host_errno_table[] initialization.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210708170550.1846343-8-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>